1. Field of the Invention
The present invention relates to a reaction apparatus for producing trichlorosilane and a method for producing trichlorosilane used in reacting metal silicon powder with hydrogen chloride gas, thereby generating trichlorosilane.
2. Description of Related Art
Trichlorosilane (SiHCl3) used as a raw material for producing extremely high purity silicon having a purity greater than 99.999999999% is produced, for example, by reacting metal silicon powder (Si) of about 98% in purity with hydrogen chloride gas (HCl).
As described above, as a reaction apparatus for generating trichlorosilane through reactions of metal silicon powder with hydrogen chloride gas, there is proposed an apparatus which is provided with an apparatus body into which metal silicon powder is supplied and an ejection port for ejecting hydrogen chloride gas into the apparatus body from the bottom part of the apparatus body. Metal silicon powder, the grain size of which is relatively small, for example, 1000 μm or less, is supplied into the apparatus body, hydrogen chloride gas is ejected from the bottom part of the apparatus body to fluidize the metal silicon powder, thereby the metal silicon powder is brought into contact with the hydrogen chloride gas sufficiently to produce trichlorosilane through the reactions thereof.
In this case, in order to facilitate the reaction of metal silicon powder with hydrogen chloride gas, it is effective to disperse the hydrogen chloride gas uniformly into the apparatus body without any maldistribution of flow.
Conventionally, in order to disperse hydrogen chloride gas, a porous nozzle having a plurality of ejection ports is used as an ejection member. However, when the porous nozzle or the like is used, there is a case where the ejection ports may be clogged with metal silicon powder. For this reason, such a problem exists in that there is a failure in uniform contact of metal silicon powder with hydrogen chloride gas, non-uniform reactions proceed inside the reaction apparatus, thereby generating silicon tetrachloride in an increased quantity to result in a decreased efficiency of generating trichlorosilane. There is also a problem in that reactions proceed locally to result in a rise in temperature at a part concerned and the reaction apparatus itself may be broken. There is another problem in that due to maldistribution of hydrogen chloride gas flow, grains of metal silicon powder collides to cause wear on the inner surface of the apparatus body, thermometers, internal parts or the like.
Therefore, as a method for preventing the above-described clogging and also dispersing hydrogen chloride gas, Japanese Patent No. 2519094 disclosed an apparatus in which a flat-plate shaped holed piece layer is disposed on the upper side of a nozzle and a granule layer is also disposed on the flat-plate shaped holed piece layer. As described above, the flat-plate shaped holed piece layer is disposed, thereby suppressing the metal silicon powder from entering into the ejection ports of the nozzle, preventing the ejection ports from being clogged, thus making it possible to prevent non-uniform ejection of hydrogen chloride gas due to wear and subsequent enlargement of the ejection ports resulting from the metal silicon powder. Further, hydrogen chloride gas is ejected toward the metal silicon powder through the flat-plate shaped holed piece layer, by which the hydrogen chloride gas can be uniformly and widely dispersed and therefore uniformly fluidized without any maldistribution of flow.
Incidentally, in the reaction apparatus for producing trichlorosilane described in Japanese Patent No. 2519094, the lower layer in which flat-plate shaped holed pieces are stacked and the upper layer in which ball members are stacked on the flat-plate shaped holed piece layer are installed so as to be separated. Thus, there is a case where in the flat-plate shaped holed piece layer, the flat-plate shaped holed pieces are stacked on each other in a state in which they are individually laid down and the flat-plate shaped holed pieces are arranged so as to be firmly attached to each other. When a plurality of these holed pieces are firmly attached to each other, no clearance is secured between the flat-plate shaped holed pieces, thus resulting in a fear that the effect of dispersion of hydrogen chloride gas may not be sufficiently obtained.
Further, since there has been a great increase in demand for high-purity silicon, there is now a need for more efficient production of trichlorosilane than before.